1. Technical Field
The present disclosure relates to a random number generating device, in particular, to a random number generating device making a generated random signal have white noise characteristic by feedback.
2. Description of Related Art
Referring to FIG. 1A, FIG. 1A is a functional block diagram illustrating a conventional random number generating device. As illustrated in FIG. 1A, the conventional random number generating device 9 primarily comprises a high frequency generator 90, a low frequency generator 92 and a D flip-flop 94. In practical operation, a random signal RN generated from the D flip-flop 94 is generated by accessing a high frequency signal NOISE_SIG generated from the high frequency generator 90 based on a clock signal CLK generated from the low frequency generator 92. However, since the clock signal CLK generated from the low frequency generator 92 is a stable low frequency signal, the characteristic of the random signal RN is determined by the characteristic of the high frequency signal NOISE_SIG.
For generating a set of random signals RN having diversity of die-to-die, referring to FIG. 1B. FIG. 1B is another functional block diagram illustrating a conventional random number generating device. As illustrated in FIG. 1B, the conventional random number generating device 9′ comprises a high frequency generator 90, a first low frequency generator 96, a second low frequency generator 92, a D flip-flop 94 and a mixer 98. The random number generating device 9′ generates a mixed signal Mix_noise by mixing a high frequency signal H_noise generated from the high frequency generator 90 and a low frequency signal L_noise generated from the first low frequency generator 96 via the mixer 98. Then, the D flip-flop 94 accesses the mixed signal Mix_noise based on a clock signal CLK generated from the second low frequency generator 92 and outputs the a random signal RN via an output end thereof.
Referring to FIG. 2A and FIG. 2B, FIG. 2A is a spectrum schematic diagram of a mixed signal in the random number generating device in FIG. 1B; FIG. 2B is a spectrum schematic diagram of a random signal in the random number generating device in FIG. 1B. As illustrated in FIG. 2A and FIG. 2B, the spectrum of the mixed signal Mix_noise still shows certain regularity so that the spectrum of the random signal RN also shows regularity with little variation. Therefore, although the random signal RN generated from the conventional random number generating device 9 meets the requirement for diversity of die-to-die, the random signal RN still cannot meet the requirement for white noise characteristic and diversity of time-to-time.